The present invention generally relates to transportation. More particularly, the invention relates to the transportation of people or goods in transit corridors made up of both railway and roadway sections, by means of vehicles that are equipped to operate with equal facility on railway rails and road surfaces, and that are propelled using a traction wheel system. The invention also relates to other conveyances, such as bicycles, which can be propelled using a similar traction wheel system.
The need exists for a transportation system that provides efficient, flexible and ecologically sound carriage of persons and goods between various locations. As an example, people work in cities but live in the suburbs, typically commuting along known routes and at known times, yet no flexible, efficient transportation system exists to fill even this common need. Private vehicles on roadways offer good flexibility in the choice of routes, departure points and destinations, but they are not fuel efficient when compared with other forms of transportation, and their use, en masse, causes traffic jams, environmental problems, and other undesirable consequences.
Railroad vehicles have the advantage of very high fuel efficiency, the result of the low rolling friction between the vehicle's steel wheels and the steel rails, an efficiency that is enhanced by the use of electricity for propulsion. Unfortunately, railroad routes are not flexible, offering few opportunities for route changes or the altering of departure points and destinations. The railway commuter is forced to use some other means of transportation to get to or from the fixed railway system. The usual other means is a motor vehicle, bus, taxi or the commuter's own car, making parking and transfer facilities necessary at access points along the rail line, and reducing the overall efficiency of the rail commute. Another disadvantage of railroad operation is that the low rolling friction between the steel wheels and steel rails is accompanied by limited traction as well, limiting acceleration, braking and grade climbing ability. Such low traction limits railway grades to about 3%, meaning that, to replace a grade crossing with a 15 foot clearance overpass, the railway approach ramps on each side must be 500 feet long. The 3% limit prevents new rail commuter lines from being placed on the medians of existing highways.
Buses, by contrast, offer considerable flexibility, being able to change routes, destinations and departure points according to roadway conditions and changes in ridership. Unfortunately, because the engine and drive train of a bus must produce enough power to counter high tire rolling friction while maintaining highway speeds, most buses are substantially over powered and inefficient for the slower speeds of downtown or suburban routes. Busways give buses a railway type of right of way to avoid highway traffic and delays, but they do not offer the `low-friction, high-efficiency` railway advantage. Also, busways cannot, generally, make use of highway medians. While vehicles guided by and confined to tracks require a right of way about 10 feet wide, buses require somewhat more width to allow for variations in steering through confined areas.
Bikeways are being promoted in some areas, the bicycle being the most efficient mode of transportation in terms of energy expended per passenger mile. Bicycles could at least reduce the need to use a motor vehicle to get to a railway station or a hybrid vehicle "station stop". If bicycle carrying trains and buses become available, bicycles could also reduce downtown motor vehicle usage as well. Although going to the office on a bicycle may never become popular, any means or mechanism that helps the increasing number of bicycle users "carry home the groceries" or "make it up that hill" is welcomed.
Transportation systems that combine rail and road operation exist in some cities of the world. Generally their rubber road tires simply act against the steel rails to provide traction on the railway sections of a route. Although providing greater traction than steel on steel, rubber on steel does not generate as much traction as rubber on paved surfaces. Therefore, vehicles utilizing rubber wheels on steel rails for traction realize only moderate increases in acceleration, braking and grade climbing ability when compared to conventional railway vehicles.
A number of devices have been devised to apply, or increase the traction needed to propel vehicles on rails and roads. One such device is disclosed in U.S. Pat. No. 1,889,241, to Gibson et al, wherein a roller, when moved into frictional engagement with a vehicle's drive wheel, serves to rotate a traction wheel, the traction wheel having some freedom to follow a road's surface while providing auxiliary, intermittent, traction on rough or icy roads.